[ { "id": "authors:mjp8s-4ne33", "collection": "authors", "collection_id": "mjp8s-4ne33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160317-132327182", "type": "article", "title": "Spatial patterns and source attribution of urban methane in the Los Angeles Basin", "author": [ { "family_name": "Hopkins", "given_name": "Francesca M.", "orcid": "0000-0002-6110-7675", "clpid": "Hopkins-F-M" }, { "family_name": "Kort", "given_name": "Eric A.", "orcid": "0000-0003-4940-7541", "clpid": "Kort-E-A" }, { "family_name": "Bush", "given_name": "Susan E.", "clpid": "Bush-S-E" }, { "family_name": "Ehleringer", "given_name": "James R.", "clpid": "Ehleringer-J-R" }, { "family_name": "Lai", "given_name": "Chun-Ta", "clpid": "Lai-Chun-Ta" }, { "family_name": "Blake", "given_name": "Donald R.", "clpid": "Blake-D-R" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" } ], "abstract": "Urban areas are increasingly recognized as a globally important source of methane to the atmosphere; however, the location of methane sources and relative contributions of source sectors are not well known. Recent atmospheric measurements in Los Angeles, California, USA, show that more than a third of the city's methane emissions are unaccounted for in inventories and suggest that fugitive fossil emissions are the unknown source. We made on-road measurements to quantify fine-scale structure of methane and a suite of complementary trace gases across the Los Angeles Basin in June 2013. Enhanced methane levels were observed across the basin but were unevenly distributed in space. We identified 213 methane hot spots from unknown emission sources. We made direct measurements of ethane to methane (C_2H_6/CH_4) ratios of known methane emission sources in the region, including cattle, geologic seeps, landfills, and compressed natural gas fueling stations, and used these ratios to determine the contribution of biogenic and fossil methane sources to unknown hot spots and to local urban background air. We found that 75% of hot spots were of fossil origin, 20% were biogenic, and 5% of indeterminate source. In regionally integrated air, we observed a wider range of C_2H_6/CH_4 values than observed previously. Fossil fuel sources accounted for 58\u201365% of methane emissions, with the range depending on the assumed C_2H_6/CH_4 ratio of source end-members and model structure. These surveys demonstrated the prevalence of fugitive methane emissions across the Los Angeles urban landscape and suggested that uninventoried methane sources were widely distributed and primarily of fossil origin.", "doi": "10.1002/2015JD024429", "issn": "2169-897X", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Atmospheres", "publication_date": "2016-03-16", "series_number": "5", "volume": "121", "issue": "5", "pages": "2490-2507" }, { "id": "authors:q728n-cyy35", "collection": "authors", "collection_id": "q728n-cyy35", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200529-093434827", "type": "article", "title": "The covariation of Northern Hemisphere summertime CO\u2082 with surface temperature in boreal regions", "author": [ { "family_name": "Wunch", "given_name": "D.", "orcid": "0000-0002-4924-0377", "clpid": "Wunch-D" }, { "family_name": "Wennberg", "given_name": "P. O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" }, { "family_name": "Messerschmidt", "given_name": "J.", "clpid": "Messerschmidt-J" }, { "family_name": "Parazoo", "given_name": "N. C.", "orcid": "0000-0002-4424-7780", "clpid": "Parazoo-N-C" }, { "family_name": "Toon", "given_name": "G. C.", "orcid": "0000-0003-4174-7541", "clpid": "Toon-G-C" }, { "family_name": "Deutscher", "given_name": "N. M.", "orcid": "0000-0002-2906-2577", "clpid": "Deutscher-N-M" }, { "family_name": "Keppel-Aleks", "given_name": "G.", "clpid": "Keppel-Aleks-G" }, { "family_name": "Roehl", "given_name": "C. M.", "orcid": "0000-0001-5383-8462", "clpid": "Roehl-C-M" }, { "family_name": "Randerson", "given_name": "J. T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Warneke", "given_name": "T.", "orcid": "0000-0001-5185-3415", "clpid": "Warneke-T" }, { "family_name": "Notholt", "given_name": "J.", "clpid": "Notholt-J" } ], "abstract": "We observe significant interannual variability in the strength of the seasonal cycle drawdown in northern midlatitudes from measurements of CO\u2082 made by the Total Carbon Column Observing Network (TCCON) and the Greenhouse Gases Observing Satellite (GOSAT). This variability correlates with surface temperature in the boreal regions. Using TCCON measurements, we find that the slope of the relationship between the X_(CO\u2082) seasonal cycle minima and boreal surface temperature is 1.2 \u00b1 0.7 ppm K\u207b\u00b9. Assimilations from CarbonTracker 2011 and CO\u2082 simulations using the Simple Biosphere exchange Model (SiB) transported by GEOS-Chem underestimate this covariation. Both atmospheric transport and biospheric activity contribute to the observed covariation.", "doi": "10.5194/acp-13-9447-2013", "issn": "1680-7324", "publisher": "European Geosciences Union", "publication": "Atmospheric Chemistry and Physics", "publication_date": "2013-09-26", "series_number": "18", "volume": "13", "issue": "18", "pages": "9447-9459" }, { "id": "authors:eqg5p-8k722", "collection": "authors", "collection_id": "eqg5p-8k722", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130820-092041048", "type": "article", "title": "Atmospheric Carbon Dioxide Variability in the Community Earth System Model: Evaluation and Transient Dynamics during the Twentieth and Twenty-First Centuries", "author": [ { "family_name": "Keppel-Aleks", "given_name": "Gretchen", "clpid": "Keppel-Aleks-G" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Lindsay", "given_name": "Keith", "clpid": "Lindsay-K" }, { "family_name": "Stephens", "given_name": "Britton B.", "clpid": "Stephens-B-B" }, { "family_name": "Moore", "given_name": "J. Keith", "clpid": "Moore-J-K" }, { "family_name": "Doney", "given_name": "Scott C.", "orcid": "0000-0002-3683-2437", "clpid": "Doney-S-C" }, { "family_name": "Thornton", "given_name": "Peter E.", "clpid": "Thornton-P-E" }, { "family_name": "Mahowald", "given_name": "Natalie M.", "clpid": "Mahowald-N-M" }, { "family_name": "Hoffman", "given_name": "Forrest M.", "clpid": "Hoffman-Forrest-M" }, { "family_name": "Sweeney", "given_name": "Colm", "orcid": "0000-0001-9568-0050", "clpid": "Sweeney-C" }, { "family_name": "Tans", "given_name": "Pieter P.", "clpid": "Tans-P-P" }, { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" }, { "family_name": "Wofsy", "given_name": "Steven C.", "orcid": "0000-0002-3990-6737", "clpid": "Wofsy-S-C" } ], "abstract": "Changes in atmospheric CO_2 variability during the twenty-first century may provide insight about ecosystem responses to climate change and have implications for the design of carbon monitoring programs. This paper describes changes in the three-dimensional structure of atmospheric CO_2 for several representative concentration pathways (RCPs 4.5 and 8.5) using the Community Earth System Model\u2013Biogeochemistry (CESM1-BGC). CO_2 simulated for the historical period was first compared to surface, aircraft, and column observations. In a second step, the evolution of spatial and temporal gradients during the twenty-first century was examined. The mean annual cycle in atmospheric CO_2 was underestimated for the historical period throughout the Northern Hemisphere, suggesting that the growing season net flux in the Community Land Model (the land component of CESM) was too weak. Consistent with weak summer drawdown in Northern Hemisphere high latitudes, simulated CO_2 showed correspondingly weak north\u2013south and vertical gradients during the summer. In the simulations of the twenty-first century, CESM predicted increases in the mean annual cycle of atmospheric CO_2 and larger horizontal gradients. Not only did the mean north\u2013south gradient increase due to fossil fuel emissions, but east\u2013west contrasts in CO_2 also strengthened because of changing patterns in fossil fuel emissions and terrestrial carbon exchange. In the RCP8.5 simulation, where CO_2 increased to 1150 ppm by 2100, the CESM predicted increases in interannual variability in the Northern Hemisphere midlatitudes of up to 60% relative to present variability for time series filtered with a 2\u201310-yr bandpass. Such an increase in variability may impact detection of changing surface fluxes from atmospheric observations.", "doi": "10.1175/JCLI-D-12-00589.1", "issn": "0894-8755", "publisher": "American Meteorological Society", "publication": "Journal of Climate", "publication_date": "2013-07", "series_number": "13", "volume": "26", "issue": "13", "pages": "4447-4475" }, { "id": "authors:j37bb-d7y02", "collection": "authors", "collection_id": "j37bb-d7y02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120127-072000089", "type": "article", "title": "Daily and 3\u2010hourly variability in global fire emissions and consequences for atmospheric model predictions of carbon monoxide", "author": [ { "family_name": "Mu", "given_name": "M.", "clpid": "Mu-M" }, { "family_name": "Randerson", "given_name": "J. T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "van der Werf", "given_name": "G. R.", "clpid": "van-der-Werf-G-R" }, { "family_name": "Giglio", "given_name": "L.", "clpid": "Giglio-L" }, { "family_name": "Kasibhatla", "given_name": "P.", "clpid": "Kasibhatla-P" }, { "family_name": "Morton", "given_name": "D.", "clpid": "Morton-D" }, { "family_name": "Collatz", "given_name": "G. J.", "clpid": "Collatz-G-J" }, { "family_name": "DeFries", "given_name": "R. S.", "clpid": "DeFries-R-S" }, { "family_name": "Hyer", "given_name": "E. J.", "clpid": "Hyer-E-J" }, { "family_name": "Prins", "given_name": "E. M.", "clpid": "Prins-E-M" }, { "family_name": "Griffith", "given_name": "D. W. T.", "orcid": "0000-0002-7986-1924", "clpid": "Griffith-D-W-T" }, { "family_name": "Wunch", "given_name": "D.", "orcid": "0000-0002-4924-0377", "clpid": "Wunch-D" }, { "family_name": "Toon", "given_name": "G. C.", "orcid": "0000-0003-4174-7541", "clpid": "Toon-G-C" }, { "family_name": "Sherlock", "given_name": "V.", "clpid": "Sherlock-V" }, { "family_name": "Wennberg", "given_name": "P. O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" } ], "abstract": "Attribution of the causes of atmospheric trace gas and aerosol variability often requires the use of high resolution time series of anthropogenic and natural emissions inventories. Here we developed an approach for representing synoptic- and diurnal-scale temporal variability in fire emissions for the Global Fire Emissions Database version 3 (GFED3). We disaggregated monthly GFED3 emissions during 2003\u20132009 to a daily time step using Moderate Resolution Imaging Spectroradiometer (MODIS)-derived measurements of active fires from Terra and Aqua satellites. In parallel, mean diurnal cycles were constructed from Geostationary Operational Environmental Satellite (GOES) Wildfire Automated Biomass Burning Algorithm (WF_ABBA) active fire observations. Daily variability in fires varied considerably across different biomes, with short but intense periods of daily emissions in boreal ecosystems and lower intensity (but more continuous) periods of burning in savannas. These patterns were consistent with earlier field and modeling work characterizing fire behavior dynamics in different ecosystems. On diurnal timescales, our analysis of the GOES WF_ABBA active fires indicated that fires in savannas, grasslands, and croplands occurred earlier in the day as compared to fires in nearby forests. Comparison with Total Carbon Column Observing Network (TCCON) and Measurements of Pollution in the Troposphere (MOPITT) column CO observations provided evidence that including daily variability in emissions moderately improved atmospheric model simulations, particularly during the fire season and near regions with high levels of biomass burning. The high temporal resolution estimates of fire emissions developed here may ultimately reduce uncertainties related to fire contributions to atmospheric trace gases and aerosols. Important future directions include reconciling top-down and bottom up estimates of fire radiative power and integrating burned area and active fire time series from multiple satellite sensors to improve daily emissions estimates.", "doi": "10.1029/2011JD016245", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research D", "publication_date": "2011-12-24", "volume": "116", "pages": "Art. No. D24303" }, { "id": "authors:g524t-17t78", "collection": "authors", "collection_id": "g524t-17t78", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:SMIjgrg08", "type": "article", "title": "Molecular hydrogen uptake by soils in forest, desert, and marsh ecosystems in California", "author": [ { "family_name": "Smith-Downey", "given_name": "Nicole V.", "clpid": "Smith-Downey-N-V" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Eiler", "given_name": "John M.", "clpid": "Eiler-J-M" } ], "abstract": "The mechanism and environmental controls on soil hydrogen (H_2) uptake are not well understood but are essential for understanding the atmospheric H_2 budget. Field observations of soil H_2 uptake are limited, and here we present the results from a series of measurements in forest, desert, and marsh ecosystems in southern California. We measured soil H_2 fluxes using flux chambers from September 2004 to July 2005. Mean H2 flux rates and standard deviations were \u22127.9 + \u22124.2, \u22127.6 + \u22125.3 and \u22127.5 + \u22123.4 nmol m^(\u22122) s^(\u22121) for the forest, desert, and marsh, respectively (corresponding to deposition velocities of 0.063 + \u22120.029, 0.051 + \u22120.036, 0.035 + \u22120.013 cm s^(\u22121)). Soil profile measurements showed that H_2 mixing ratios were between 3% and 51% of atmospheric levels at 10 cm and that the penetration of H_2 into deeper soil layers increased with soil drying. Soil removal experiments in the forest demonstrated that the litter layer did not actively consume H_2, the removal of this layer increased uptake by deeper soil layers, and the exposure of subsurface soil layers to ambient atmospheric H_2 levels substantially increased their rate of uptake. Similar soil removal experiments at the desert site showed that extremely dry surface soils did not consume H2 and that fluxes at the surface increased when these inactive layers were removed. We present a model of soil H_2 fluxes and show that the diffusivity of soils, along with the vertical distribution of layers that actively consume H_2 regulate surface fluxes. We found that soil organic matter, CO_2 fluxes, and ecosystem type were not strong controllers of H_2 uptake. Our experiments highlight H_2 diffusion into soils as an important limit on fluxes and that minimum moisture level is needed to initiate microbial uptake.", "doi": "10.1029/2008JG000701", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research G", "publication_date": "2008-09-23", "volume": "113", "pages": "G03037" }, { "id": "authors:trkpy-epq28", "collection": "authors", "collection_id": "trkpy-epq28", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:CHAgrl08", "type": "article", "title": "Satellite remote sounding of mid-tropospheric CO_2", "author": [ { "family_name": "Chahine", "given_name": "M. T.", "clpid": "Chahine-M-T" }, { "family_name": "Chen", "given_name": "Luke", "clpid": "Chen-Luke" }, { "family_name": "Dimotakis", "given_name": "Paul", "clpid": "Dimotakis-P-E" }, { "family_name": "Jiang", "given_name": "Xun", "orcid": "0000-0001-8932-3807", "clpid": "Jiang-Xun" }, { "family_name": "Li", "given_name": "Qinbi", "clpid": "Li-Qinbi" }, { "family_name": "Pagano", "given_name": "Thomas", "clpid": "Pagano-T-S" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" } ], "abstract": "Human activity has increased the concentration of the earth's atmospheric carbon dioxide, which plays a direct role in contributing to global warming. Mid-tropospheric CO_2 retrieved by the Atmospheric Infrared Sounder shows a substantial spatiotemporal variability that is supported by in situ aircraft measurements. The distribution of middle tropospheric CO_2 is strongly influenced by surface sources and large-scale circulations such as the mid-latitude jet streams and by synoptic weather systems, most notably in the summer hemisphere. In addition, the effects of stratosphere-troposphere exchange are observed during a final stratospheric warming event. The results provide the means to understand the sources and sinks and the lifting of CO_2 from surface layers into the free troposphere and its subsequent transport around the globe. These processes are not adequately represented in three chemistry-transport models that have been used to study carbon budgets.", "doi": "10.1029/2008GL035022", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2008-09", "series_number": "17", "volume": "35", "issue": "17", "pages": "Art. No. L17807" }, { "id": "authors:4a3pd-j1044", "collection": "authors", "collection_id": "4a3pd-j1044", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:PETpnas07", "type": "article", "title": "An atmospheric perspective on North American carbon dioxide exchange: CarbonTracker", "author": [ { "family_name": "Peters", "given_name": "Wouter", "orcid": "0000-0001-8166-2070", "clpid": "Peters-W" }, { "family_name": "Jacobson", "given_name": "Andrew R.", "clpid": "Jacobson-A-R" }, { "family_name": "Sweeney", "given_name": "Colm", "orcid": "0000-0001-9568-0050", "clpid": "Sweeney-C" }, { "family_name": "Andrews", "given_name": "Arlyn E.", "orcid": "0000-0002-8552-3999", "clpid": "Andrews-A-E" }, { "family_name": "Conway", "given_name": "Thomas J.", "clpid": "Conway-T-J" }, { "family_name": "Massarle", "given_name": "Kenneth", "clpid": "Massarle-K" }, { "family_name": "Miller", "given_name": "John B.", "clpid": "Miller-J-B" }, { "family_name": "Bruhwiler", "given_name": "Lori M. P.", "clpid": "Bruhwiler-L-M-P" }, { "family_name": "P\u00e9tron", "given_name": "Gabrielle", "clpid": "P\u00e9tron-G" }, { "family_name": "Hirsch", "given_name": "Adam I.", "clpid": "Hirsch-A-I" }, { "family_name": "Worthy", "given_name": "Douglas E. J.", "clpid": "Worthy-D-E-J" }, { "family_name": "van der Werf", "given_name": "Guido R.", "clpid": "van-der-Werf-G-R" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" }, { "family_name": "Krol", "given_name": "Maarten C.", "clpid": "Krol-M-C" }, { "family_name": "Tans", "given_name": "Pieter P.", "clpid": "Tans-P-P" } ], "abstract": "We present an estimate of net CO2 exchange between the terrestrial biosphere and the atmosphere across North America for every week in the period 2000 through 2005. This estimate is derived from a set of 28,000 CO2 mole fraction observations in the global atmosphere that are fed into a state-of-the-art data assimilation system for CO2 called CarbonTracker. By design, the surface fluxes produced in CarbonTracker are consistent with the recent history of CO2 in the atmosphere and provide constraints on the net carbon flux independent from national inventories derived from accounting efforts. We find the North American terrestrial biosphere to have absorbed \u20130.65 PgC/yr (1 petagram = 10^15 g; negative signs are used for carbon sinks) averaged over the period studied, partly offsetting the estimated 1.85 PgC/yr release by fossil fuel burning and cement manufacturing. Uncertainty on this estimate is derived from a set of sensitivity experiments and places the sink within a range of \u20130.4 to \u20131.0 PgC/yr. The estimated sink is located mainly in the deciduous forests along the East Coast (32%) and the boreal coniferous forests (22%). Terrestrial uptake fell to \u20130.32 PgC/yr during the large-scale drought of 2002, suggesting sensitivity of the contemporary carbon sinks to climate extremes. CarbonTracker results are in excellent agreement with a wide collection of carbon inventories that form the basis of the first North American State of the Carbon Cycle Report (SOCCR), to be released in 2007. All CarbonTracker results are freely available at http://carbontracker.noaa.gov.", "pmcid": "PMC2141884", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "2007-11-27", "series_number": "48", "volume": "104", "issue": "48", "pages": "18925-18930" }, { "id": "authors:s7v2j-90452", "collection": "authors", "collection_id": "s7v2j-90452", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140702-100545630", "type": "article", "title": "New constraints on Northern Hemisphere growing season net flux", "author": [ { "family_name": "Yang", "given_name": "Z.", "clpid": "Yang-Z" }, { "family_name": "Washenfelder", "given_name": "R. A.", "orcid": "0000-0002-8106-3702", "clpid": "Washenfelder-R-A" }, { "family_name": "Keppel-Aleks", "given_name": "G.", "clpid": "Keppel-Aleks-G" }, { "family_name": "Krakauer", "given_name": "N. Y.", "clpid": "Krakauer-N-Y" }, { "family_name": "Randerson", "given_name": "J. T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Tans", "given_name": "P. P.", "clpid": "Tans-P-P" }, { "family_name": "Sweeney", "given_name": "C.", "orcid": "0000-0001-9568-0050", "clpid": "Sweeney-C" }, { "family_name": "Wennberg", "given_name": "P. O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" } ], "abstract": "Observations of the column-averaged dry molar mixing ratio of CO_2 above both Park Falls, Wisconsin and Kitt Peak, Arizona, together with partial columns derived from aircraft profiles over Eurasia and North America are used to estimate the seasonal integral of net ecosystem exchange (NEE) between the atmosphere and the terrestrial biosphere in the Northern Hemisphere. We find that NEE is \u223c25% larger than predicted by the Carnegie Ames Stanford Approach (CASA) model. We show that the estimates of NEE may have been biased low by too weak vertical mixing in the transport models used to infer seasonal changes in Northern Hemisphere CO_2 mass from the surface measurements of CO_2 mixing ratio.", "doi": "10.1029/2007GL029742", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2007-06-23", "series_number": "12", "volume": "34", "issue": "12", "pages": "Art. No. L12807" }, { "id": "authors:ph2sz-ab029", "collection": "authors", "collection_id": "ph2sz-ab029", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181128-113350185", "type": "article", "title": "Regional patterns of radiocarbon and fossil fuel-derived CO_2 in surface air across North America", "author": [ { "family_name": "Hsueh", "given_name": "Diana Y.", "clpid": "Hsueh-Diana-Y" }, { "family_name": "Krakauer", "given_name": "Nir Y.", "clpid": "Krakauer-N-Y" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Xu", "given_name": "Xiaomei", "clpid": "Xu-Xiaomei" }, { "family_name": "Trumbore", "given_name": "Susan E.", "clpid": "Trumbore-S-E" }, { "family_name": "Southon", "given_name": "John R.", "orcid": "0000-0001-6168-6235", "clpid": "Southon-J-R" } ], "abstract": "Radiocarbon levels in annual plants provide a means to map out regional and continental\u2010scale fossil fuel plumes in surface air. We collected corn (Zea mays) across North America during the summer of 2004. Plants from mountain regions of western North America showed the smallest influence of fossil fuel\u2010derived CO_2 with a mean \u0394^(14)C of 66.3\u2030 \u00b11.7\u2030. Plants from eastern North America and from the Ohio\u2010Maryland region showed a larger fossil fuel influence with a mean \u0394^(14)C of 58.8\u2030 \u00b1 3.9\u2030 and 55.2\u2030 \u00b1 2.3\u2030, respectively, corresponding to 2.7 ppm \u00b1 1.5 ppm and 4.3 ppm \u00b1 1.0 ppm of added fossil fuel CO_2 relative to the mountain west. A model\u2013data comparison suggests that surveys of annual plant \u0394^(14)C can provide a useful test of atmospheric mixing in transport models that are used to estimate the spatial distribution of carbon sources and sinks.", "doi": "10.1029/2006gl027032", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2007-01", "series_number": "2", "volume": "34", "issue": "2", "pages": "Art. No. L02816" }, { "id": "authors:ek3z5-6a745", "collection": "authors", "collection_id": "ek3z5-6a745", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141118-090640921", "type": "article", "title": "The Impact of Boreal Forest Fire on Climate Warming", "author": [ { "family_name": "Randerson", "given_name": "J. T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Liu", "given_name": "H.", "clpid": "Liu-H" }, { "family_name": "Flanner", "given_name": "M. G.", "clpid": "Flanner-M-G" }, { "family_name": "Chambers", "given_name": "S. D.", "clpid": "Chambers-S-D" }, { "family_name": "Jin", "given_name": "Y.", "clpid": "Jin-Y" }, { "family_name": "Hess", "given_name": "P. G.", "clpid": "Hess-P-G" }, { "family_name": "Pfister", "given_name": "G.", "clpid": "Pfister-G-G" }, { "family_name": "Mack", "given_name": "M. C.", "clpid": "Mack-M-C" }, { "family_name": "Treseder", "given_name": "K. K.", "clpid": "Treseder-K-K" }, { "family_name": "Welp", "given_name": "L. R.", "orcid": "0000-0001-7125-0478", "clpid": "Welp-L-R" }, { "family_name": "Chapin", "given_name": "F. S.", "clpid": "Chapin-F-S" }, { "family_name": "Harden", "given_name": "J. W.", "clpid": "Harden-J-W" }, { "family_name": "Goulden", "given_name": "M. L.", "orcid": "0000-0002-9379-3948", "clpid": "Goulden-M-L" }, { "family_name": "Lyons", "given_name": "E.", "clpid": "Lyons-E" }, { "family_name": "Neff", "given_name": "J. C.", "clpid": "Neff-J-C" }, { "family_name": "Schuur", "given_name": "E. A. G.", "clpid": "Schuur-E-A-G" }, { "family_name": "Zender", "given_name": "C. S.", "clpid": "Zender-C-S" } ], "abstract": "We report measurements and analysis of a boreal forest fire, integrating the effects of greenhouse gases, aerosols, black carbon deposition on snow and sea ice, and postfire changes in surface albedo. The net effect of all agents was to increase radiative forcing during the first year (34 \u00b1 31 Watts per square meter of burned area), but to decrease radiative forcing when averaged over an 80-year fire cycle (\u20132.3 \u00b1 2.2 Watts per square meter) because multidecadal increases in surface albedo had a larger impact than fire-emitted greenhouse gases. This result implies that future increases in boreal fire may not accelerate climate warming.", "doi": "10.1126/science.1132075", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2006-11-17", "series_number": "5802", "volume": "314", "issue": "5802", "pages": "1130-1132" }, { "id": "authors:52rjj-m0a12", "collection": "authors", "collection_id": "52rjj-m0a12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121120-142146542", "type": "article", "title": "Temperature and moisture dependence of soil H_2 uptake measured in the laboratory", "author": [ { "family_name": "Smith-Downey", "given_name": "Nicole V.", "clpid": "Smith-Downey-N-V" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Eiler", "given_name": "John M.", "clpid": "Eiler-J-M" } ], "abstract": "The soil sink of molecular hydrogen is the largest and most uncertain term in the global atmospheric H_2 budget. Lack of information about the mechanisms regulating this sink limits our ability to predict how atmospheric H_2 may respond to future changes in climate or anthropogenic emissions. Here we present the results from a series of laboratory experiments designed to systematically evaluate and describe the temperature and soil moisture dependence of H_2 uptake by soils from boreal forest and desert ecosystems. We observed substantial H2 uptake between \u22124\u00b0C and 0\u00b0C, a broad temperature optimum between 20\u00b0C and 30\u00b0C, a soil moisture optimum at approximately 20% saturation, and inhibition of uptake at both low and high soil moisture. A sigmoidal function described the temperature response of H_2 uptake by soils between \u221215\u00b0C and 40\u00b0C. Based on our results, we present a framework for a model of the soil H_2 sink.", "doi": "10.1029/2006GL026749", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2006-07-25", "series_number": "14", "volume": "33", "issue": "14", "pages": "Art. No. L14813" }, { "id": "authors:hgfqx-cp238", "collection": "authors", "collection_id": "hgfqx-cp238", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191011-091358305", "type": "article", "title": "Consequences of Incomplete Surface Energy Balance Closure for CO_2 Fluxes from Open-Path CO_2/H_2O Infrared Gas Analysers", "author": [ { "family_name": "Liu", "given_name": "Heping", "clpid": "Liu-Heping" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Lindfors", "given_name": "Jamie", "clpid": "Lindfors-J" }, { "family_name": "Massman", "given_name": "William J.", "clpid": "Massman-W-J" }, { "family_name": "Foken", "given_name": "Thomas", "clpid": "Foken-T" } ], "abstract": "We present an approach for assessing the impact of systematic biases in measured energy fluxes on CO_2 flux estimates obtained from open-path eddy-covariance systems. In our analysis, we present equations to analyse the propagation of errors through the Webb, Pearman, and Leuning (WPL) algorithm [Quart. J. Roy. Meteorol. Soc. 106, 85\u2013100, 1980] that is widely used to account for density fluctuations on CO_2 flux measurements. Our results suggest that incomplete energy balance closure does not necessarily lead to an underestimation of CO_2 fluxes despite the existence of surface energy imbalance; either an overestimation or underestimation of CO_2 fluxes is possible depending on local atmospheric conditions and measurement errors in the sensible heat, latent heat, and CO_2 fluxes. We use open-path eddy-covariance fluxes measured over a black spruce forest in interior Alaska to explore several energy imbalance scenarios and their consequences for CO_2 fluxes.", "doi": "10.1007/s10546-005-9047-z", "issn": "0006-8314", "publisher": "Springer", "publication": "Boundary-Layer Meteorology", "publication_date": "2006-07", "series_number": "1", "volume": "120", "issue": "1", "pages": "65-85" }, { "id": "authors:ktbw3-33j54", "collection": "authors", "collection_id": "ktbw3-33j54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181130-105900662", "type": "article", "title": "Asimow, Jahren, and Randerson receive 2005 James B. Macelwane Medal", "author": [ { "family_name": "Eiler", "given_name": "John", "clpid": "Eiler-J-M" }, { "family_name": "Asimow", "given_name": "Paul D.", "orcid": "0000-0001-6025-8925", "clpid": "Asimow-P-D" }, { "family_name": "Dove", "given_name": "Patricia M.", "clpid": "Dove-P-M" }, { "family_name": "Jahnren", "given_name": "A. Hope", "clpid": "Jahnren-A-H" }, { "family_name": "Trumbore", "given_name": "Susan", "clpid": "Trumbore-S-E" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" } ], "abstract": "It is my great pleasure to present my friend and colleague, Paul Asimow, recipient of one of this year's three James B. Macelwane Medals. Paul is a petrologist interested in the origins and evolution of basaltic magmas, and he is being recognized for a series of profoundly insightful papers on the energetics of decompression melting and how it controls the compositions of the oceanic crust and upper mantle.\n\nThe significance of what Paul has done comes from the simplicity of the question that first inspired him: How should we describe the way the mantle melts as it upwells during convection? The importance of the problem is obvious; this is how the Earth makes most of its crust, and so it is the starting point for most of geology But does it sound like something we already understand? Wasn't I taught this as an undergraduate? Paul's first and perhaps most important contribution was to recognize, as a second\u2010year graduate student working with Ed Stolper [California Institute of Technology (Caltech),Pasadena],that the explanation of mantle melting we were telling each other was a Rube Goldberg device masquerading as physical theory.", "doi": "10.1029/2006eo040005", "issn": "0096-3941", "publisher": "American Geophysical Union", "publication": "Eos", "publication_date": "2006-01-24", "series_number": "4", "volume": "87", "issue": "4", "pages": "40-41" }, { "id": "authors:rcny2-k5882", "collection": "authors", "collection_id": "rcny2-k5882", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181128-140625713", "type": "article", "title": "Influence of reduced carbon emissions and oxidation on the distribution of atmospheric CO_2: Implications for inversion analyses", "author": [ { "family_name": "Suntharalingam", "given_name": "Parvadha", "clpid": "Suntharalingam-P" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Krakauer", "given_name": "Nir", "clpid": "Krakauer-N-Y" }, { "family_name": "Logan", "given_name": "Jennifer A.", "clpid": "Logan-J-A" }, { "family_name": "Jacob", "given_name": "Daniel J.", "orcid": "0000-0002-6373-3100", "clpid": "Jacob-D-J" } ], "abstract": "Recent inverse analyses constraining carbon fluxes using atmospheric CO_2 observations have assumed that the CO_2 source from atmospheric oxidation of reduced carbon is released at the surface rather than distributed globally in the atmosphere. This produces a bias in the estimates of surface fluxes. We used a three\u2010dimensional (3D) atmospheric chemistry model (GEOS\u2010CHEM) to evaluate the magnitude of this effect on modeled concentrations and flux estimates. We find that resolving the 3D structure of the atmospheric CO_2 source, as opposed to emitting this reduced carbon as CO_2 at the surface, yields a decrease in the modeled annual mean interhemispheric gradient (N\u2010S) of 0.21 ppm. Larger adjustments (up to \u22120.6 ppm) are apparent on a regional basis in and downwind of regions of high reduced carbon emissions. We used TransCom3 annual mean simulations from three transport models to evaluate the implications for inversion estimates. The main impacts are systematic decreases in estimates of northern continental land uptake (i.e., by 0.22 to 0.26 Pg C yr^(\u22121)), and reductions in tropical land carbon efflux with smaller changes over oceans and in the Southern Hemisphere. These adjustments represent a systematic bias in flux estimates, accounting for changes of 9 to 27% in the estimated northern land CO_2 sink for the three models evaluated here. Our results highlight the need for a realistic description of reduced carbon emission and oxidation processes in deriving inversion estimates of CO_2 surface fluxes.", "doi": "10.1029/2005gb002466", "issn": "0886-6236", "publisher": "American Geophysical Union", "publication": "Global Biogeochemical Cycles", "publication_date": "2005-12", "series_number": "4", "volume": "19", "issue": "4", "pages": "Art. No. GB4003" }, { "id": "authors:99e0y-jsq91", "collection": "authors", "collection_id": "99e0y-jsq91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181128-140625630", "type": "article", "title": "Changes in the surface energy budget after fire in boreal ecosystems of interior Alaska: An annual perspective", "author": [ { "family_name": "Liu", "given_name": "Heping", "clpid": "Liu-Heping" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Lindfors", "given_name": "Jamie", "clpid": "Lindfors-J" }, { "family_name": "Chapin", "given_name": "F. Stuart, III", "clpid": "Chapin-F-S-III" } ], "abstract": "Understanding links between the disturbance regime and regional climate in boreal regions requires observations of the surface energy budget from ecosystems in various stages of secondary succession. While several studies have characterized fire\u2010induced differences in surface energy fluxes from boreal ecosystems during summer months, much less is known about these differences over the full annual cycle. Here we measured components of the surface energy budget (including both radiative and turbulent fluxes) at three sites from a fire chronosequence in interior Alaska for a 1\u2010year period. Our sites consisted of large burn scars resulting from fires in 1999, 1987, and \u223c1920 (hereinafter referred to as the 3\u2010, 15\u2010, and 80\u2010year sites, respectively). Vegetation cover consisted primarily of bunch grasses at the 3\u2010year site, aspen and willow at the 15\u2010year site, and black spruce at the 80\u2010year site. Annual net radiation declined by 31% (17 W m^(\u22122)) for both the 3\u2010 and the 15\u2010year sites as compared with the 80\u2010year site (which had an annual mean of 55 W m^(\u22122)). Annual sensible heat fluxes were reduced by an even greater amount, by 55% at the 3\u2010year site and by 52% at the 15\u2010year site as compared with the 80\u2010year site (which had an annual mean of 21 W m^(\u22122)). Absolute differences between the postfire ecosystems and the mature black spruce forest for both net radiation and sensible heat fluxes were greatest during spring (because of differences in snow cover and surface albedo), substantial during summer and winter, and relatively small during fall. Fire\u2010induced disturbance also initially reduced annual evapotranspiration (ET). Annual ET decreased by 33% (99 mm yr^(\u22121)) at the 3\u2010year site as compared with the 80\u2010year site (which had an annual flux of 301 mm yr^(\u22121)). Annual ET at the 15\u2010year site (283 mm yr^(\u22121)) was approximately the same as that from the 80\u2010year site, even though the 15\u2010year site had substantially higher ET during July. Our study suggests that differences in annual ET between deciduous and conifer stands may be smaller than that inferred solely from summer observations. This study provides a direct means to validate land surface processes in global climate models attempting to capture vegetation\u2010climate feedbacks in northern terrestrial regions.", "doi": "10.1029/2004jd005158", "issn": "2169-897X", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Atmospheres", "publication_date": "2005-07-16", "series_number": "D13", "volume": "110", "issue": "D13", "pages": "Art. No. D13101" }, { "id": "authors:sp2dq-bqk83", "collection": "authors", "collection_id": "sp2dq-bqk83", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160930-104900408", "type": "article", "title": "Using generalized cross-validation to select parameters in inversions for regional carbon fluxes", "author": [ { "family_name": "Krakauer", "given_name": "Nir Y.", "clpid": "Krakauer-N-Y" }, { "family_name": "Schneider", "given_name": "Tapio", "orcid": "0000-0001-5687-2287", "clpid": "Schneider-T" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Olsen", "given_name": "Seth C.", "clpid": "Olsen-S-C" } ], "abstract": "[1] Estimating CO_2 fluxes from the pattern of atmospheric CO_2 concentrations with atmospheric transport models is an ill-posed inverse problem, whose solution is stabilized using prior information. Weights assigned to prior information and to CO_2 concentrations at different locations are quantified by parameters that are not well known, and differences in the choice of these parameters contribute to differences among published estimates of the regional partitioning of CO_2 fluxes. Following the TransCom 3 protocol to estimate CO_2 fluxes for 1992\u20131996, we find that the partitioning of the CO_2 sink between land and oceans and between North America and Eurasia depends on parameters that quantify the relative weight given to prior flux estimates and the extent to which CO_2 concentrations at different stations are differentially weighted. Parameter values that minimize an estimated prediction error can be chosen by generalized cross-validation (GCV). The GCV parameter values yield fluxes in northern regions similar to those obtained with the TransCom parameter values, but the GCV fluxes are smaller in the poorly constrained equatorial and southern regions.", "doi": "10.1029/2004GL020323", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2004-10", "series_number": "19", "volume": "31", "issue": "19", "pages": "Art. No. L19108" }, { "id": "authors:h9xk9-4hv53", "collection": "authors", "collection_id": "h9xk9-4hv53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140701-091835991", "type": "article", "title": "Recent changes in the air-sea gas exchange of methyl chloroform", "author": [ { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" }, { "family_name": "Peacock", "given_name": "Synte", "orcid": "0000-0002-1046-025X", "clpid": "Peacock-S" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Bleck", "given_name": "Rainer", "clpid": "Bleck-R" } ], "abstract": "Atmospheric measurements of methyl chloroform provide important constraints on the rate of oxidation of hydrocarbons in Earth's atmosphere. Estimates of the loss of methyl chloroform to the oceans play a small but important role in these calculations. Here, we examine the ocean-atmosphere interaction of methyl chloroform in a global ocean model. Contrary to previous assumptions, these simulations suggest that the high-latitude oceans are currently a source of this chemical to the atmosphere. If confirmed, this finding alters estimates of the change in the atmospheric oxidation rate of hydrocarbons. We highlight the potential usefulness of methyl chloroform as a tracer of ocean circulation.", "doi": "10.1029/2004GL020476", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2004-08-24", "series_number": "16", "volume": "31", "issue": "16", "pages": "Art. No. L16112" }, { "id": "authors:8qzzt-evf32", "collection": "authors", "collection_id": "8qzzt-evf32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181128-140625539", "type": "article", "title": "Trends in high northern latitude soil freeze and thaw cycles from 1988 to 2002", "author": [ { "family_name": "Smith", "given_name": "Nicole V.", "clpid": "Smith-Downey-N-V" }, { "family_name": "Saatchi", "given_name": "Sassan S.", "clpid": "Saatchi-S-S" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" } ], "abstract": "In boreal and tundra ecosystems the freeze state of soils limits rates of photosynthesis and respiration. Here we develop a technique to identify the timing of freeze and thaw transitions of high northern latitude land areas using satellite data from the Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave/Imager (SSM/I). Our results indicate that in Eurasia there was a trend toward earlier thaw dates in tundra (\u22123.3 \u00b1 1.8 days/decade) and larch biomes (\u22124.5 \u00b1 1.8 days/decade) over the period 1988\u20132002. In North America there was a trend toward later freeze dates in evergreen conifer forests by 3.1 \u00b1 1.2 days/decade that led, in part, to a lengthening of the growing season by 5.1 \u00b1 2.9 days/decade. The growing season length in North American tundra increased by 5.4 \u00b1 3.1 days/decade. Despite the trend toward earlier thaw dates in Eurasian larch forests, the growing season length did not increase because of parallel changes in timing of the fall freeze (\u22125.4 \u00b1 2.1 days/decade), which led to a forward shift of the growing season. Thaw timing was negatively correlated with surface air temperatures in the spring, whereas freeze timing was positively correlated with surface air temperatures in the fall, suggesting that surface air temperature is one of several factors that determines the timing of soil thaw and freeze. The high spatial resolution, frequent temporal coverage, and duration of the SMMR and SSM/I satellite records makes them suitable for rigorous time series analysis and change detection in northern terrestrial ecosystems.", "doi": "10.1029/2003jd004472", "issn": "2169-897X", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Atmospheres", "publication_date": "2004-06-27", "series_number": "D12", "volume": "109", "issue": "D12", "pages": "Art. No. D12101" }, { "id": "authors:8d31g-zmv94", "collection": "authors", "collection_id": "8d31g-zmv94", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181128-140625455", "type": "article", "title": "Differences between surface and column atmospheric CO_2 and implications for carbon cycle research", "author": [ { "family_name": "Olsen", "given_name": "Seth C.", "clpid": "Olsen-S-C" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" } ], "abstract": "We used a three\u2010dimensional atmospheric transport model to investigate several aspects of column CO_2 that are important for the design of new satellite\u2010based observation systems and for the interpretation of observations collected by Sun\u2010viewing spectrometers. These aspects included the amplitude of the diurnal cycle and how it is related to surface fluxes, the amplitude and phase of the seasonal cycle, and the magnitude of the north\u2010south hemispheric gradient. In our simulation, we found that column CO_2 had less variability than surface CO_2 on all scales. The annual mean column CO_2 north\u2010south gradient and seasonal cycle amplitude were approximately one half of their surface counterparts and the column CO_2 diurnal amplitude rarely exceeded 1 ppm. A 1 Gt C yr^(\u22121) Northern Hemisphere carbon sink decreased the north\u2010south column CO_2 gradient by \u223c0.4 ppm.", "doi": "10.1029/2003jd003968", "issn": "2169-897X", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Atmospheres", "publication_date": "2004-01-27", "series_number": "D2", "volume": "109", "issue": "D2", "pages": "Art. No. D02301" }, { "id": "authors:9zdap-dxn55", "collection": "authors", "collection_id": "9zdap-dxn55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141202-130150892", "type": "article", "title": "Continental-Scale Partitioning of Fire Emissions During the 1997 to 2001 El Ni\u00f1o/La Ni\u00f1a Period", "author": [ { "family_name": "van der Werf", "given_name": "Guido R.", "clpid": "van-der-Werf-G-R" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Collatz", "given_name": "G. James", "clpid": "Collatz-G-J" }, { "family_name": "Giglio", "given_name": "Louis", "clpid": "Giglio-L" }, { "family_name": "Kasibhatla", "given_name": "Prasad S.", "clpid": "Kasibhatla-P-S" } ], "abstract": "During the 1997 to 1998 El Ni\u00f1o, drought conditions triggered widespread increases in fire activity, releasing CH_4 and CO_2 to the atmosphere. We evaluated the contribution of fires from different continents to variability in these greenhouse gases from 1997 to 2001, using satellite-based estimates of fire activity, biogeochemical modeling, and an inverse analysis of atmospheric CO anomalies. During the 1997 to 1998 El Ni\u00f1o, the fire emissions anomaly was 2.1 \u00b1 0.8 petagrams of carbon, or 66 \u00b1 24% of the CO_2 growth rate anomaly. The main contributors were Southeast Asia (60%), Central and South America (30%), and boreal regions of Eurasia and North America (10%).", "doi": "10.1126/science.1090753", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2004-01-02", "series_number": "5654", "volume": "303", "issue": "5654", "pages": "73-76" }, { "id": "authors:5vhy3-r4220", "collection": "authors", "collection_id": "5vhy3-r4220", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181127-141320617", "type": "article", "title": "Top-down estimates of global CO sources using MOPITT measurements", "author": [ { "family_name": "Arellano", "given_name": "Avelino F., Jr.", "clpid": "Arellano-A-F-Jr" }, { "family_name": "Kasibhatla", "given_name": "Prasad S.", "clpid": "Kasibhatla-P-S" }, { "family_name": "Giglio", "given_name": "Louis", "clpid": "Giglio-L" }, { "family_name": "van der Werf", "given_name": "Guido R.", "clpid": "van-der-Werf-G-R" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" } ], "abstract": "We present a synthesis inversion of CO emissions from various geographical regions and for various source categories for the year 2000 using CO retrievals from the MOPITT (Measurements of Pollution in the Troposphere) instrument. We find a large discrepancy between our top\u2010down estimates and recent bottom\u2010up estimates of CO emissions from fossil fuel/biofuel (FFBF) use in Asia. A key conclusion of this study is that CO emissions in East Asia (EAS) are about a factor of 1.8\u20132 higher than recent bottom\u2010up estimates.", "doi": "10.1029/2003gl018609", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2004-01", "series_number": "1", "volume": "31", "issue": "1", "pages": "Art. No. L01104" }, { "id": "authors:a4mh2-x8f69", "collection": "authors", "collection_id": "a4mh2-x8f69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140701-093514734", "type": "article", "title": "The Orbiting Carbon Observatory (OCO) mission", "author": [ { "family_name": "Crisp", "given_name": "D.", "orcid": "0000-0002-4573-9998", "clpid": "Crisp-D" }, { "family_name": "Randerson", "given_name": "J. T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Wennberg", "given_name": "P. O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" }, { "family_name": "Yung", "given_name": "Y. L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" }, { "family_name": "Kuang", "given_name": "Z.", "clpid": "Kuang-Zhiming" } ], "abstract": "The Orbiting Carbon Observatory (OCO) mission will make the first global, space-based measurements of atmospheric carbon dioxide (CO_2) with the precision, resolution, and coverage needed to characterize CO_2 sources and sinks on regional scales. The measurement approach and instrument specifications were determined through an analysis of existing carbon cycle data and a series of observing system simulation experiments. During its 2-year mission, OCO will fly in a 1:15 PM sun-synchronous orbit with a 16-day ground-track repeat time, just ahead of the EOS Aqua platform. It will carry a single instrument that incorporates three bore-sighted high-resolution spectrometers designed to measure reflected sunlight in the 0.76-\u03bcm O_2 A-band and in the CO_2 bands at 1.61 and 2.06 \u03bcm. Soundings recorded in these three bands will be used to retrieve the column-averaged CO_2 dry air mole fraction (X_(CO)_2). A comprehensive validation program was included in the mission to ensure that the space-based X_(CO)_2 measurements have precisions of \u223c0.3% (1 ppm) on regional scales. OCO measurements will be used in global synthesis inversion and data assimilation models to quantify CO_2 sources and sinks. While OCO will have a nominal lifetime of only 2 years, it will serve as a pathfinder for future long-term CO_2 monitoring missions.", "doi": "10.1016/j.asr.2003.08.062", "issn": "0273-1177", "publisher": "Elsevier", "publication": "Advances in Space Research", "publication_date": "2004", "series_number": "4", "volume": "34", "issue": "4", "pages": "700-709" }, { "id": "authors:wnxy2-rpz61", "collection": "authors", "collection_id": "wnxy2-rpz61", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181128-140624798", "type": "article", "title": "Do volcanic eruptions enhance or diminish net primary production? Evidence from tree rings", "author": [ { "family_name": "Krakauer", "given_name": "Nir Y.", "clpid": "Krakauer-N-Y" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" } ], "abstract": "Low growth rates of atmospheric CO_2 were observed following the 1991 Pinatubo (Luzon) volcanic eruption. One hypothesis for this CO_2 anomaly is that since diffuse light is more efficiently used by forests than direct light, the increase in the diffuse fraction of sunlight due to scattering by volcanic sulfur aerosol in the years following the eruption substantially increased forest net primary production (NPP). However, other observations suggest a decrease in northern forest NPP because of the cooler conditions following the eruption. Here we used a global database of dated tree ring widths (which correlate with forest NPP) to test this hypothesis. Ice core records of sulfur deposition allowed us to identify the timing and magnitude of 23 Pinatubo\u2010scale eruptions since 1000 CE. We found a significant decrease in ring width for trees in middle to high northern latitudes (north of 45\u00b0N) following eruption sulfur peaks. Decreases in tree ring widths were in the range of 2\u20138% and persisted for \u223c8 years following sulfur peaks, with minima at around 4\u20136 years. Ring width changes at lower latitudes in the Northern Hemisphere (30\u00b0N to 45\u00b0N) and in the Southern Hemisphere (30\u00b0S to 56\u00b0S) were not significant. In the tropics (30\u00b0N to 30\u00b0S) the paucity of tree ring records did not permit the evaluation of NPP changes. Given that elevated aerosol levels and summer cooling last only \u223c2\u20133 years after an eruption, the persistence of declines in northern tree growth for up to 8 years after eruptions implies some additional mechanism that links these shorter\u2010lived global eruption effects to sustained changes in tree physiology, biogeochemistry, or microclimate. At least for this sample of trees, the beneficial effect of aerosol light scattering appears to be entirely offset by the deleterious effect of eruption\u2010induced climate change.", "doi": "10.1029/2003gb002076", "issn": "0886-6236", "publisher": "American Geophysical Union", "publication": "Global Biogeochemical Cycles", "publication_date": "2003-12", "series_number": "4", "volume": "17", "issue": "4", "pages": "Art. No. 1118" }, { "id": "authors:f9b8w-f7s93", "collection": "authors", "collection_id": "f9b8w-f7s93", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181127-145121921", "type": "article", "title": "Contribution of soil respiration in tropical, temperate, and boreal forests to the ^(18)O enrichment of atmospheric O_2", "author": [ { "family_name": "Angert", "given_name": "Alon", "clpid": "Angert-A" }, { "family_name": "Barkan", "given_name": "Eugeni", "clpid": "Barkan-E" }, { "family_name": "Barnett", "given_name": "Bruce", "clpid": "Barnett-B" }, { "family_name": "Brugnoli", "given_name": "Enrico", "clpid": "Brugnoli-E" }, { "family_name": "Davidson", "given_name": "Eric A.", "clpid": "Davidson-E-A" }, { "family_name": "Fessenden", "given_name": "Julianna", "clpid": "Fessenden-J-E" }, { "family_name": "Maneepong", "given_name": "Somsak", "clpid": "Maneepong-S" }, { "family_name": "Panapitukkul", "given_name": "Nipa", "clpid": "Panapitukkul-N" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Savage", "given_name": "Kathleen", "clpid": "Savage-K" }, { "family_name": "Yakir", "given_name": "Dan", "clpid": "Yakir-D" }, { "family_name": "Luz", "given_name": "Boaz", "clpid": "Luz-B" } ], "abstract": "The ^(18)O content of atmospheric O_2 is an important tracer for past changes in the biosphere. Its quantitative use depends on knowledge of the discrimination against ^(18)O associated with the various O_2 consumption processes. Here we evaluated, for the first time, the in situ ^(18)O discrimination associated with soil respiration in natural ecosystems. The discrimination was estimated from the measured [O_2] and \u03b4^(18)O of O_2 in the soil\u2010air. The discriminations that were found are 10.1 \u00b1 1.5\u2030, 17.8 \u00b1 1.0\u2030, and 22.5 \u00b1 3.6\u2030, for tropical, temperate, and boreal forests, respectively, 17.9 \u00b1 2.5\u2030 for Mediterranean woodland, and 15.4 \u00b1 1.6\u2030 for tropical shrub land. Current understanding of the isotopic composition of atmospheric O_2 is based on the assumption that the magnitude of the fractionation in soil respiration is identical to that of dark respiration through the cytochrome pathway alone (\u223c18\u2030). The discrimination we found in the tropical sites is significantly lower, and is explained by slow diffusion in soil aggregates and root tissues that limits the O_2 concentration in the consumption sites. The high discrimination in the boreal sites may be the result of high engagement of the alternative oxidase pathway (AOX), which has high discrimination associated with it (\u223c27\u2030). The intermediate discrimination (\u223c18\u2030) in the temperate and Mediterranean sites can be explained by the opposing effects of AOX and diffusion limitation that cancel out. Since soil respiration is a major component of the global oxygen uptake, the contribution of large variations in the discrimination, observed here, to the global Dole Effect should be considered in global scale studies.", "doi": "10.1029/2003gb002056", "issn": "0886-6236", "publisher": "American Geophysical Union", "publication": "Global Biogeochemical Cycles", "publication_date": "2003-09", "series_number": "3", "volume": "17", "issue": "3", "pages": "Art. No. 1089" }, { "id": "authors:qba87-dn208", "collection": "authors", "collection_id": "qba87-dn208", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121031-135240882", "type": "article", "title": "Concentration and \u03b4D of molecular hydrogen in boreal forests:\n Ecosystem-scale systematics of atmospheric H_2", "author": [ { "family_name": "Rahn", "given_name": "Thom", "clpid": "Rahn-T" }, { "family_name": "Eiler", "given_name": "John M.", "clpid": "Eiler-J-M" }, { "family_name": "Kitchen", "given_name": "Nami", "clpid": "Kitchen-N" }, { "family_name": "Fessenden", "given_name": "Julianna E.", "clpid": "Fessenden-J-E" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" } ], "abstract": "We examined the concentration and \u03b4D of atmospheric H2 in a boreal forest in interior Alaska to investigate the systematics of high latitude soil uptake at ecosystem scale. Samples collected during nighttime inversions exhibited vigorous H_2 uptake, with concentration negatively correlated with the concentration of CO_2 (\u22120.8 to \u22121.2 ppb H_2 per ppm CO_2) and negatively correlated with \u03b4D of H_2. We derived H_2 deposition rates of between 2 to 12 nmol m^(\u22122) s^(\u22121). These rates are comparable to those observed in lower latitude ecosystems. We also derive an average fractionation factor, \u03b1 = D:H_(residual)/D:H_(consumed) = 0.94 \u00b1 0.01 and suggestive evidence that \u03b1 depends on forest maturity. Our results show that high northern latitude soils are a significant sink of molecular hydrogen indicating that the record of atmospheric H_2 may be sensitive to changes in climate and land use.", "doi": "10.1029/2002GL015118", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2002-09-15", "series_number": "18", "volume": "29", "issue": "18", "pages": "Art. No. 1888" }, { "id": "authors:468gv-zkq50", "collection": "authors", "collection_id": "468gv-zkq50", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141027-091212856", "type": "article", "title": "Carbon isotope discrimination of arctic and boreal biomes inferred from remote atmospheric measurements and a biosphere-atmosphere model", "author": [ { "family_name": "Randerson", "given_name": "J. T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Still", "given_name": "C. J.", "clpid": "Still-C-J" }, { "family_name": "Ball\u00e9", "given_name": "J. J.", "clpid": "Ball\u00e9-J-J" }, { "family_name": "Fung", "given_name": "I. Y.", "clpid": "Fung-Inez-Y" }, { "family_name": "Doney", "given_name": "S. C.", "orcid": "0000-0002-3683-2437", "clpid": "Doney-S-C" }, { "family_name": "Tans", "given_name": "P. P.", "clpid": "Tans-P-P" }, { "family_name": "Conway", "given_name": "T. J.", "clpid": "Conway-T-J" }, { "family_name": "White", "given_name": "J. W. C.", "clpid": "White-J-W-C" }, { "family_name": "Vaughn", "given_name": "B.", "clpid": "Vaughn-B" }, { "family_name": "Suits", "given_name": "N.", "clpid": "Suits-N" }, { "family_name": "Denning", "given_name": "A. S.", "clpid": "Denning-A-S" } ], "abstract": "Estimating discrimination against ^(13)C during photosynthesis at landscape, regional, and biome scales is difficult because of large-scale variability in plant stress, vegetation composition, and photosynthetic pathway. Here we present estimates of ^(13)C discrimination for northern biomes based on a biosphere-atmosphere model and on National Oceanic and Atmospheric Administration Climate Monitoring and Diagnostics Laboratory and Institute of Arctic and Alpine Research remote flask measurements. With our inversion approach, we solved for three ecophysiological parameters of the northern biosphere (^(13)C discrimination, a net primary production light use efficiency, and a temperature sensitivity of heterotrophic respiration (a Q10 factor)) that provided a best fit between modeled and observed \u03b4^(13)C and CO_2. In our analysis we attempted to explicitly correct for fossil fuel emissions, remote C4 ecosystem fluxes, ocean exchange, and isotopic disequilibria of terrestrial heterotrophic respiration caused by the Suess effect. We obtained a photosynthetic discrimination for arctic and boreal biomes between 19.0 and 19.6\u2030. Our inversion analysis suggests that Q10 and light use efficiency values that minimize the cost function covary. The optimal light use efficiency was 0.47 gC MJ^(\u22121) photosynthetically active radiation, and the optimal Q10 value was 1.52. Fossil fuel and ocean exchange contributed proportionally more to month-to-month changes in the atmospheric growth rate of \u03b4^(13)C and CO_2 during winter months, suggesting that remote atmospheric observations during the summer may yield more precise estimates of the isotopic composition of the biosphere.", "doi": "10.1029/2001GB001435", "issn": "0886-6236", "publisher": "American Geophysical Union", "publication": "Global Biogeochemical Cycles", "publication_date": "2002-09", "series_number": "3", "volume": "16", "issue": "3", "pages": "Art. No. 1028" }, { "id": "authors:fjv7b-mvm48", "collection": "authors", "collection_id": "fjv7b-mvm48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181128-093337809", "type": "article", "title": "Trends in North American net primary productivity derived from satellite observations, 1982-1998", "author": [ { "family_name": "Hicke", "given_name": "Jeffrey A.", "clpid": "Hicke-J-A" }, { "family_name": "Asner", "given_name": "Gregory P.", "clpid": "Asner-G-P" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Tucker", "given_name": "Compton", "clpid": "Tucker-C-J" }, { "family_name": "Los", "given_name": "Sietse", "clpid": "Los-S-O" }, { "family_name": "Birdsey", "given_name": "Richard", "clpid": "Birdsey-R" }, { "family_name": "Jenkins", "given_name": "Jennifer C.", "clpid": "Jenkins-J-C" }, { "family_name": "Field", "given_name": "Christopher", "clpid": "Field-C-B" } ], "abstract": "Net primary productivity (NPP) in North America was computed for the years 1982\u20131998 using the Carnegie\u2010Ames\u2010Stanford approach (CASA) carbon cycle model. CASA was driven by a new, corrected satellite record of the normalized difference vegetation index at 8\u2010km spatial resolution. Regional trends in the 17\u2010year NPP record varied substantially across the continent. Croplands and grasslands of the Central Plains and eastern Canadian forests experienced summer increases in NPP. Peak NPP trends in Alaska and western Canada occurred in late spring or early summer, suggesting an earlier onset of the growing season in these regions. Forests and woodlands of the southeastern United States showed NPP increases in spring and fall, also suggesting an increase in the length of the growing season. An analysis of climate variables showed that summer precipitation increased in the Central Plains, indicating that climate changes probably play some role in increasing NPP in this region, though intensive management of agricultural ecosystems has also increased productivity. Similarly, increased summer precipitation possibly increased NPP in eastern Canada, but another possible explanation is forest recovery after insect damage. NPP in the southeastern United States increased in the absence of climate variation. Much of this region consists of aggressively managed forests, with young stand ages and intensive silviculture resulting in increased NPP. The high latitudes of western Canada and Alaska experienced spring warming that could have increased NPP in late spring or early summer.", "doi": "10.1029/2001gb001550", "issn": "0886-6236", "publisher": "American Geophysical Union", "publication": "Global Biogeochemical Cycles", "publication_date": "2002-06", "series_number": "2", "volume": "16", "issue": "2", "pages": "2-1" }, { "id": "authors:s4qdh-zwz45", "collection": "authors", "collection_id": "s4qdh-zwz45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181128-095140922", "type": "article", "title": "Satellite-derived increases in net primary productivity across North America, 1982-1998", "author": [ { "family_name": "Hicke", "given_name": "Jeffrey A.", "clpid": "Hicke-J-A" }, { "family_name": "Asner", "given_name": "Gregory P.", "clpid": "Asner-G-P" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Tucker", "given_name": "Compton", "clpid": "Tucker-C-J" }, { "family_name": "Los", "given_name": "Sietse", "clpid": "Los-S-O" }, { "family_name": "Birdsey", "given_name": "Richard", "clpid": "Birdsey-R" }, { "family_name": "Jenkins", "given_name": "Jennifer C.", "clpid": "Jenkins-J-C" }, { "family_name": "Field", "given_name": "Christopher", "clpid": "Field-C-B" }, { "family_name": "Holland", "given_name": "Elisabeth", "clpid": "Holland-E" } ], "abstract": "We used a new 17\u2010year, high spatial resolution satellite record and a carbon cycle model to explore how changing net primary productivity (NPP) contributed to a proposed carbon (C) sink in North America. We found a small but significant increase in NPP, 0.03 Pg C yr^(\u22122) or 8% over 17 years, that could explain a substantial fraction of the C sink. The largest increases occurred in the central and southeastern United States, eastern Canada, and northwestern North America, and were consistent with NPP trends derived from forest inventories and crop yields. Interannual NPP variability was small, implying that the large interannual variability in the C sink found in previous studies were driven by changes in heterotrophic respiration.", "doi": "10.1029/2001GL013578", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2002-05-15", "series_number": "10", "volume": "29", "issue": "10", "pages": "69-1" }, { "id": "authors:wjc2g-1p970", "collection": "authors", "collection_id": "wjc2g-1p970", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150331-093118332", "type": "article", "title": "Towards robust regional estimates of CO_2 sources and sinks using atmospheric transport models", "author": [ { "family_name": "Gurney", "given_name": "Kevin Robert", "orcid": "0000-0001-9218-7164", "clpid": "Gurney-K-R" }, { "family_name": "Randerson", "given_name": "James", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" } ], "abstract": "Information about regional carbon sources and sinks can be derived from variations in observed atmospheric CO_2 concentrations via inverse modelling with atmospheric tracer transport models. A consensus has not yet been reached regarding the size and distribution of regional carbon fluxes obtained using this approach, partly owing to the use of several different atmospheric transport models. Here we report estimates of surface\u2013atmosphere CO_2 fluxes from an intercomparison of atmospheric CO_2 inversion models (the TransCom 3 project), which includes 16 transport models and model variants. We find an uptake of CO_2 in the southern extratropical ocean less than that estimated from ocean measurements, a result that is not sensitive to transport models or methodological approaches. We also find a northern land carbon sink that is distributed relatively evenly among the continents of the Northern Hemisphere, but these results show some sensitivity to transport differences among models, especially in how they respond to seasonal terrestrial exchange of CO_2. Overall, carbon fluxes integrated over latitudinal zones are strongly constrained by observations in the middle to high latitudes. Further significant constraints to our understanding of regional carbon fluxes will therefore require improvements in transport models and expansion of the CO_2 observation network within the tropics.", "doi": "10.1038/415626a", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2002-02-07", "series_number": "6872", "volume": "415", "issue": "6872", "pages": "626-630" }, { "id": "authors:kws76-kgd50", "collection": "authors", "collection_id": "kws76-kgd50", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141118-085746566", "type": "article", "title": "Biospheric Primary Production During an ENSO Transition", "author": [ { "family_name": "Behrenfeld", "given_name": "Michael J.", "clpid": "Behrenfeld-M-J" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "McClain", "given_name": "Charles R.", "clpid": "McClain-C-R" }, { "family_name": "Feldman", "given_name": "Gene C.", "clpid": "Feldman-G-C" }, { "family_name": "Los", "given_name": "Sietse O.", "clpid": "Los-S-O" }, { "family_name": "Tucker", "given_name": "Compton J.", "clpid": "Tucker-C-J" }, { "family_name": "Falkowski", "given_name": "Paul J.", "clpid": "Falkowski-P-J" }, { "family_name": "Field", "given_name": "Christopher B.", "clpid": "Field-C-B" }, { "family_name": "Frouin", "given_name": "Robert", "clpid": "Frouin-R" }, { "family_name": "Esaias", "given_name": "Wayne E.", "clpid": "Esaias-W-E" }, { "family_name": "Kolber", "given_name": "Dorota D.", "clpid": "Kolber-D-D" }, { "family_name": "Pollack", "given_name": "Nathan H.", "clpid": "Pollack-N-H" } ], "abstract": "The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) provides global monthly measurements of both oceanic phytoplankton chlorophyll biomass and light harvesting by land plants. These measurements allowed the comparison of simultaneous ocean and land net primary production (NPP) responses to a major El Ni\u00f1o to La Ni\u00f1a transition. Between September 1997 and August 2000, biospheric NPP varied by 6 petagrams of carbon per year (from 111 to 117 petagrams of carbon per year). Increases in ocean NPP were pronounced in tropical regions where El Ni\u00f1o\u2013Southern Oscillation (ENSO) impacts on upwelling and nutrient availability were greatest. Globally, land NPP did not exhibit a clear ENSO response, although regional changes were substantial.", "doi": "10.1126/science.1055071", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2001-03-30", "series_number": "5513", "volume": "291", "issue": "5513", "pages": "2594-2597" }, { "id": "authors:19663-xp862", "collection": "authors", "collection_id": "19663-xp862", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181128-140624899", "type": "article", "title": "The contribution of terrestrial sources and sinks to trends in the seasonal cycle of atmospheric carbon dioxide", "author": [ { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Thompson", "given_name": "Matthew V.", "clpid": "Thompson-M-V" }, { "family_name": "Conway", "given_name": "Thomas J.", "clpid": "Conway-T-J" }, { "family_name": "Fung", "given_name": "Inez Y.", "clpid": "Fung-Inez-Y" }, { "family_name": "Field", "given_name": "Christopher B.", "clpid": "Field-C-B" } ], "abstract": "We characterized decadal changes in the amplitude and shape of the seasonal cycle of atmospheric CO_2 with three kinds of analysis. First, we calculated the trends in the seasonal cycle of measured atmospheric CO_2 at observation stations in the National Oceanic and Atmospheric Administration Climate Monitoring and Diagnostic Laboratory network. Second, we assessed the impact of terrestrial ecosystems in various localities on the mean seasonal cycle of CO_2 at observation stations using the Carnegie\u2010Ames\u2010Stanford Approach terrestrial biosphere model and the Goddard Institute for Space Studies (GISS) atmospheric tracer transport model. Third, we used the GISS tracer model to quantify the contribution of terrestrial sources and sinks to trends in the seasonal cycle of atmospheric CO_2 for the period 1961\u20131990, specifically examining the effects of biomass burning, emissions from fossil fuel combustion, and regional increases in net primary production (NPP). Our analysis supports results from previous studies that indicate a significant positive increase in the amplitude of the seasonal cycle of CO_2 at Arctic and subarctic observation stations. For stations north of 55\u00b0N the amplitude increased at a mean rate of 0.66% yr^(\u22121) from 1981 to 1995. From the analysis of ecosystem impacts on the mean seasonal cycle we find that tundra, boreal forest, and other northern ecosystems are responsible for most of the seasonal variation in CO_2 at stations north of 55\u00b0N. The effects of tropical biomass burning on trends in the seasonal cycle are minimal at these stations, probably because of strong vertical convection in equatorial regions. From 1981 to 1990, fossil fuel emissions contributed a trend of 0.20% yr^(\u22121) to the seasonal cycle amplitude at Mauna Loa and less than 0.10% yr^(\u22121) at stations north of 55\u00b0N. To match the observed amplitude increases at Arctic and subarctic stations with NPP increases, we find that north of 30\u00b0N a 1.7 Pg C yr^(\u22121) terrestrial sink would be required. In contrast, over regions south of 30\u00b0N, even large NPP increases and accompanying terrestrial sinks would be insufficient to account for the increase in high\u2010latitude amplitudes.", "doi": "10.1029/97gb02268", "issn": "0886-6236", "publisher": "American Geophysical Union", "publication": "Global Biogeochemical Cycles", "publication_date": "1997-12", "series_number": "4", "volume": "11", "issue": "4", "pages": "535-560" }, { "id": "authors:p5gt0-r0x56", "collection": "authors", "collection_id": "p5gt0-r0x56", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181128-140624981", "type": "article", "title": "Interannual variation in global-scale net primary production: Testing model estimates", "author": [ { "family_name": "Malmstr\u00f6m", "given_name": "Carolyn M.", "clpid": "Malmstr\u00f6m-C-M" }, { "family_name": "Thompson", "given_name": "Matthew V.", "clpid": "Thompson-M-V" }, { "family_name": "Juday", "given_name": "Glenn P.", "clpid": "Juday-G-P" }, { "family_name": "Los", "given_name": "Sietse O.", "clpid": "Los-S-O" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Field", "given_name": "Christopher B.", "clpid": "Field-C-B" } ], "abstract": "Testing estimates of year\u2010to\u2010year variation in global net primary production (NPP) poses some challenges. Large\u2010scale, multiyear records of production are not readily available for natural systems but are for agricultural systems. We use records of agricultural yields at selected sites to test NPP estimates produced by CASA, a global\u2010scale production model driven by both meteorological data and the satellite\u2010derived normalized difference vegetation index (NDVI). We also test estimates produced by the Miami model, which has underlain several analyses of biosphere response to interannual changes in climate. In addition, we test estimates against tree ring data for one boreal site for which data from both coniferous and deciduous species were available. The agricultural tests demonstrate that CASA can reasonably estimate interannual variation in production. The Miami model estimates variation more poorly. However, differences in NDVI\u2010processing algorithms substantially affect CASA's estimates of interannual variation. Of the four versions tested, the FASIR NDVI most closely reproduced yield data and showed the least correlation with changes in equatorial crossing time of the National Oceanic and Atmospheric Administration satellites. One issue raised is the source of the positive trends evident in CASA's NDVI\u2010based estimates of global NPP. The existence of these trends is consistent with potential stimulation of terrestrial production by factors such as CO2 enrichment, N fertilization, or temperature warming, but the magnitude of the global trends seen is significantly greater than suggested by constraints imposed by atmospheric fluxes.", "doi": "10.1029/97gb01419", "issn": "0886-6236", "publisher": "American Geophysical Union", "publication": "Global Biogeochemical Cycles", "publication_date": "1997-09", "series_number": "3", "volume": "11", "issue": "3", "pages": "367-392" }, { "id": "authors:afqgt-bb463", "collection": "authors", "collection_id": "afqgt-bb463", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181128-140625081", "type": "article", "title": "Change in net primary production and heterotrophic respiration: How much is necessary to sustain the terrestrial carbon sink?", "author": [ { "family_name": "Thompson", "given_name": "Matthew V.", "clpid": "Thompson-M-V" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Malmstr\u00f6m", "given_name": "Carolyn M.", "clpid": "Malmstr\u00f6m-C-M" }, { "family_name": "Field", "given_name": "Christopher B.", "clpid": "Field-C-B" } ], "abstract": "In recent years, the chief approaches used to describe the terrestrial carbon sink have been either (1) inferential, based on changes in the carbon content of the atmosphere and other elements of the global carbon cycle, or (2) mechanistic, applying our knowledge of terrestrial ecology to ecosystem scale processes. In this study, the two approaches are integrated by determining the change in terrestrial properties necessary to match inferred change in terrestrial carbon storage. In addition, a useful mathematical framework is developed for understanding the important features of the terrestrial carbon sink. The Carnegie\u2010Ames\u2010Stanford Approach (CASA) biosphere model, a terrestrial carbon cycle model that uses a calibrated, semimechanistic net primary production model and a mechanistic plant and soil carbon turnover model, is employed to explore carbon turnover dynamics in terms of the specific features of terrestrial ecosystems that are most important for the potential development of a carbon sink and to determine the variation in net primary production (NPP) necessary to satisfy various carbon sink estimates. Given the existence of a stimulatory mechanism acting on terrestrial NPP, net ecosystem uptake is expected to be largest where NPP is high and the turnover of carbon through plants and the soil is slow. In addition, it was found that (1) long\u2010term, climate\u2010induced change in heterotrophic respiration is not as important in determining long\u2010term carbon exchange as is change in NPP and (2) the terrestrial carbon sink rate is determined not by the cumulative increase in production over some pre\u2010industrial baseline, but rather by the rate of increase in production over the industrial period.", "doi": "10.1029/96gb01667", "issn": "0886-6236", "publisher": "American Geophysical Union", "publication": "Global Biogeochemical Cycles", "publication_date": "1996-12", "series_number": "4", "volume": "10", "issue": "4", "pages": "711-726" }, { "id": "authors:th8b8-dka57", "collection": "authors", "collection_id": "th8b8-dka57", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181128-140625184", "type": "article", "title": "Substrate limitations for heterotrophs: Implications for models that estimate the seasonal cycle of atmospheric CO_2", "author": [ { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Thompson", "given_name": "Matthew V.", "clpid": "Thompson-M-V" }, { "family_name": "Malmstrom", "given_name": "Carolyn M.", "clpid": "Malmstr\u00f6m-C-M" }, { "family_name": "Field", "given_name": "Christopher B.", "clpid": "Field-C-B" }, { "family_name": "Fung", "given_name": "Inez Y.", "clpid": "Fung-Inez-Y" } ], "abstract": "We examine the sensitivity of the seasonal cycle of heterotrophic respiration to model estimates of litterfall seasonality, herbivory, plant allocation, tissue chemistry, and land use. As a part of this analysis, we compare heterotrophic respiration models based solely on temperature and soil moisture controls (zero\u2010order models) with models that depend on available substrate as well (first\u2010order models). As indicators of regional and global CO_2 exchange, we use maps of monthly global net ecosystem production, growing season net flux (GSNF), and simulated atmospheric CO_2 concentrations from an atmospheric tracer transport model. In one first\u2010order model, CASA, variations on the representation of the seasonal flow of organic matter from plants to heterotrophs can increase global GSNF as much as 60% (5.7 Pg C yr^(\u22121)) above estimates obtained from a zero\u2010order model. Under a new first\u2010order scheme that includes separate seasonal dynamics for leaf litterfall, fine root mortality, coarse woody debris, and herbivory, we observe an increase in GSNF of 8% (0.7 Pg C yr^(\u22121)) over that predicted by the zero\u2010order model. The increase in seasonality of CO2 exchange in first\u2010order models reflects the dynamics of labile litter fractions; specifically, the rapid decomposition of a pulse of labile leaf and fine root litter that enters the heterotrophic community primarily from the middle to the end of the growing season shifts respiration outside the growing season. From the perspective of a first\u2010order model, we then explore the consequences of land use change and winter temperature anomalies on the amplitude of the seasonal cycle of atmospheric CO_2. Agricultural practices that accelerate decomposition may drive a long\u2010term increase in the amplitude, independent of human impacts on plant production. Consideration of first\u2010order litter decomposition dynamics may also help explain year\u2010to\u2010year variation in the amplitude.", "doi": "10.1029/96gb01981", "issn": "0886-6236", "publisher": "American Geophysical Union", "publication": "Global Biogeochemical Cycles", "publication_date": "1996-12", "series_number": "4", "volume": "10", "issue": "4", "pages": "585-602" }, { "id": "authors:5zgfp-4kv20", "collection": "authors", "collection_id": "5zgfp-4kv20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181128-140625266", "type": "article", "title": "Terrestrial ecosystem production: A process model based on global satellite and surface data", "author": [ { "family_name": "Potter", "given_name": "Christopher S.", "clpid": "Potter-C-S" }, { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Field", "given_name": "Christopher B.", "clpid": "Field-C-B" }, { "family_name": "Matson", "given_name": "Pamela A.", "clpid": "Matson-P-A" }, { "family_name": "Vitousek", "given_name": "Peter M.", "clpid": "Vitousek-P-M" }, { "family_name": "Mooney", "given_name": "Harold A.", "clpid": "Mooney-H-A" }, { "family_name": "Klooster", "given_name": "Steven A.", "clpid": "Klooster-S-A" } ], "abstract": "This paper presents a modeling approach aimed at seasonal resolution of global climatic and edaphic controls on patterns of terrestrial ecosystem production and soil microbial respiration. We use satellite imagery (Advanced Very High Resolution Radiometer and International Satellite Cloud Climatology Project solar radiation), along with historical climate (monthly temperature and precipitation) and soil attributes (texture, C and N contents) from global (1\u00b0) data sets as model inputs. The Carnegie\u2010Ames\u2010Stanford approach (CASA) Biosphere model runs on a monthly time interval to simulate seasonal patterns in net plant carbon fixation, biomass and nutrient allocation, litterfall, soil nitrogen mineralization, and microbial CO2 production. The model estimate of global terrestrial net primary production is 48 Pg C yr^(\u22121) with a maximum light use efficiency of 0.39 g C MJ^(\u22121) PAR. Over 70% of terrestrial net production takes place between 30\u00b0N and 30\u00b0S latitude. Steady state pools of standing litter represent global storage of around 174 Pg C (94 and 80 Pg C in nonwoody and woody pools, respectively), whereas the pool of soil C in the top 0.3 m that is turning over on decadal time scales comprises 300 Pg C. Seasonal variations in atmospheric CO_2 concentrations from three stations in the Geophysical Monitoring for Climate Change Flask Sampling Network correlate significantly with estimated net ecosystem production values averaged over 50\u00b0\u201380\u00b0 N, 10\u00b0\u201330\u00b0 N, and 0\u00b0\u201310\u00b0 N.", "doi": "10.1029/93gb02725", "issn": "0886-6236", "publisher": "American Geophysical Union", "publication": "Global Biogeochemical Cycles", "publication_date": "1993-12", "series_number": "4", "volume": "7", "issue": "4", "pages": "811-841" } ]